On hybrid electric vehicles (HEV) and stop-start vehicles, an internal combustion engine (ICE) may shut-down or deactivate during selected conditions. Shutting down the engine may save fuel by avoiding certain conditions, such as idling conditions, for example. When this happens, the crankshaft and camshafts of the engine may stop in unknown positions of the engine cycle. In order to restart the engine, the position of the cams/pistons may be determined so that sequential and accurate fueling, and spark timing, may be provided to obtain reliable low emissions starts. As such, precise and timely knowledge of engine piston and cam positions during the start may enable coordination of the spark timing and fuel delivery in the engine.
Some methods of piston or engine position determination rely on a crankshaft timing wheel with a finite number of teeth and a gap to provide synchronization in coordination with camshaft measurements. Because the crankshaft position information is typically produced using a toothed wheel with a missing tooth, an engine control module can determine relative engine position to each cylinder. The crankshaft rotates twice per engine cycle, so to uniquely identify the engine position information for the crankshaft is combined with a cylinder identification (CID). When restarting an engine, the engine control module therefore typically waits for a determination of the engine position before commencing sequential fuel injection, which incurs a delay time in the reactivation process. One example is shown by U.S. Pat. No. 7,765,980, where engine position is identified via a crankshaft angle sensor.
The inventors herein have recognized issues with such approaches. For example, depending on engine temperature, the amount of time to identify crankshaft position relative to camshaft position can vary. Such variability in determining the relative positioning between the camshaft and crankshaft (in order to identify engine and piston positions) can lead to reduced ability in achieving and maintaining fast synchronization, reliable combustion, and reduced emissions. Further, any delays in identifying engine position can also delay engine starting. When restarting the engine in response to a vehicle launch request, such delays then translate to delays in vehicle response, reducing customer satisfaction.
In one example approach, some of the above issues may be addressed by a method comprising operating a laser ignition device in an engine cylinder and synchronizing fuel delivery based on a laser sensed engine position, and igniting an air and fuel mixture in the cylinder with the laser ignition device. In this way, it may be possible to take advantage of a laser ignition system to increase an accuracy of engine position identification (via cam and piston position measurements), such as during engine starting. For example, such an approach may provide faster and more accurate information on engine/piston position, velocity, etc. By identifying such information earlier during engine cranking (or even before cranking), faster synchronization with the camshaft may be achieved leading to earlier fuel delivery and engine combustion. An advantage of the above aspect of the invention is faster average engine starting time as well as improved customer satisfaction, improved fuel economy, and reduced emissions.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.